Straightening Something That Requires A Little Finesse And A Lot Of Tonnage

[jackieschmidt]

One of our customers got a boat into the bank and bent the Starboard Rudder. The shipyard cut the Stock out of the blade last night so we could straighten it and rebuild the bearing journals. The Stock is 8“ diameter with 8 3/4 diameter SS journals.

I used our 350 ton rig.

 

[jelenko]

How was it straightened? The big 'J' hooks come from underneath but the 'axle' appears to be bowed upward.

 

[hogpatrol]

That looks like old ladle crane hooks or did you make them?

 

[jackieschmidt]

That looks like old ladle crane hooks or did you make them?

Similar, but those and the strong back are custom water cut from T-1 plate

 

[jackieschmidt]

How was it straightened? The big 'J' hooks come from underneath but the 'axle' appears to be bowed upward.

I’m not quite sure what you mean.

 

[Walt Krafft]

Ok now it is straight. Wont it want to bend again??

 

[DShortt]

How was it straightened? The big 'J' hooks come from underneath but the 'axle' appears to be bowed upward.

There's a hydraulic ram between the J-hooks. It's positioned to apply pressure to the area where the bend is most significant. J-hooks are there to prevent creating a bend in another area.

I understand the basic principle. Wouldn't dare claim to have done something like this.

Nice work!

 

[jackieschmidt]

Ok now it is straight. Wont it want to bend again??

Not unless the Captain decides to bounce it off the bank again.

 

[jelenko]

I’m not quite sure what you mean.

DShortt covered it. I saw but didn't perceive the thing between the two hooks.

 

[jackieschmidt]

DShortt covered it. I saw but didn't perceive the thing between the two hooks.

You can’t see it, but the straightening rig is hanging off of a overhead crane.
The arms are adjustable so I can apply tonnage exactly where I want it and make the piece bend where I want it.

This is a job where the requirements are “get it pointing straight toward the bottom”. When we straighten propeller shafts, the requirements are more stringent, since you are not dealing with “visually straight” but in thousandths of an inch of runout.

We have fI’ve of these rigs, which we designed and built. A small one that is 150 tons, another that is 250 tons, this one at 350, another that has a 500 ton capacity, and the largest is 750 tons.
They operate off of a typical 10,000 psi Enerpac Electric Pump, which you can see in the bottom right of the first picture.

 

[topclass2017]

another great post Jackie. Always like seeing precision work on big stuff

 

[jelenko]

You can’t see it, but the straightening rig is hanging off of a overhead crane.
The arms are adjustable so I can apply tonnage exactly where I want it and make the piece bend where I want it.

This is a job where the requirements are “get it pointing straight toward the bottom”. When we straighten propeller shafts, the requirements are more stringent, since you are not dealing with “visually straight” but in thousandths of an inch of runout.

We have fI’ve of these rigs, which we designed and built. A small one that is 150 tons, another that is 250 tons, this one at 350, another that has a 500 ton capacity, and the largest is 750 tons.
They operate off of a typical 10,000 psi Enerpac Electric Pump, which you can see in the bottom right of the first picture.

Is there any 'spring back' in the shaft? I.e., does it have to be bent slightly the other way so it relaxes to being straight?

 

[Fast14riot]

Any bend between the bearing journals? Doesn't look like it, they always bend low, but I have seen bent rudder shafts bow between bearings.

 

[jackieschmidt]

Is there any 'spring back' in the shaft? I.e., does it have to be bent slightly the other way so it relaxes to being straight?

Yes. That is part of the trick.
Most of the time you will have to “bend” a piece considerably past the actual straight because of spring back.
Keep in mind, this process is not just hit it once with the tonnage and be done. the first time thing you have to do is ascertain exactly where the bend starts. As @Fast14riot just noted, often it can be bent between the journals as well. You have to ”work it out” so to speak.

We have a gage on the pump that tells me exactly how many PSI I am exerting, I get an idea through trial exactly what it is taking to move the metal. Every piece of steel can be a little different.

With this particular Rudder Stock, it was taking upwards of 7000 psi on the gage to straighten. With the spread on the arms that I had here, that means it was taking about 280 tons to move the metal.

One of the things about straightening items with a rig such as this is it is as much of an art as anything. Years of doing this has taught me, and several of my men, exactly how to, and where to, apply the tonnage for best results.

 

[JMA]

Jackie I love it when you show things like this
My entire carrier was machinist and maintenance mechanic in heavy industry
So I know what is involved in this work even thou its different in a lot aspects to what I did
Hope you keep posting things like this

 

[AccelR8]

I think the Savage factory does barrels that way.

 

[Uncle Bruce]

Yes. That is part of the trick.
Most you will have to “bend” a piece considerably past the actual straight because of spring back.
keep in mind, this process is not just hit it once with the tonnage and be done. the first time thing you have to do is ascertain exactly where the bend starts. As @Fast14riot just noted, often it can be bent between the journals as well. You have to ”work it out” so to speak.

We have a gage on the pump that tells me exactly how many PSI I am exerting, I get an idea through trial exactly what it is taking to move the metal. Every piece of steel can be a little different.

With this particular Rudder Stock, it was taking upwards of 7000 psi on the gage to straighten. With the spread on the arms that I had here, that means it was taking about 280 tons to move the metal.

One of the things about straighteningitems with a rig such as this is it is as muc of an art as anything. Years of doing this has taught me, and several of my men, exactly how to, and where to, apply the tonnage for best results.

It is like straightening an aluminum arrow, a lot of experience and a little bit of luck goes a long way.

 

[Kracken McGraw]

Yes. That is part of the trick.
Most you will have to “bend” a piece considerably past the actual straight because of spring back.
keep in mind, this process is not just hit it once with the tonnage and be done. the first time thing you have to do is ascertain exactly where the bend starts. As @Fast14riot just noted, often it can be bent between the journals as well. You have to ”work it out” so to speak.

We have a gage on the pump that tells me exactly how many PSI I am exerting, I get an idea through trial exactly what it is taking to move the metal. Every piece of steel can be a little different.

With this particular Rudder Stock, it was taking upwards of 7000 psi on the gage to straighten. With the spread on the arms that I had here, that means it was taking about 280 tons to move the metal.

One of the things about straightening items with a rig such as this is it is as much of an art as anything. Years of doing this has taught me, and several of my men, exactly how to, and where to, apply the tonnage for best results.

Jackie, I was curious if you ever apply any heat while doing this?

 

[Jesswil61]

My back hurts just thinking about having to move, handle and set up this equipment.

 

[danny]

How was it straightened? The big 'J' hooks come from underneath but the 'axle' appears to be bowed upward.

The press section is pushing down on the upward bow

Danny